OK in need of some help here. First some history. Back in January i developed a missfire. Had autozone scan codes and it was misfire number 4 cylinder and lean condition bank 1. Found the elbow in the PCV hose was cracked and replaced that. Since it was due a plug change I ordered a set of Global coils off ebay and replaced all coils and plugs with motorcraft. Truck ran great after and no codes came back. About 2 months later the truck started to develop a miss under light loads, never set a code. The miss (stumble) continued to get slightly worse and did not start until the engine warmed up. I decided that maybe one of teh new coils was bad and breaking down when it got hot. Since I had no idea which one, I decided to replace them with the ones I removed. Decided to replace the front 2 on passenger side first since they were easiest. After that truck ran fine no more miss. This lasted about about a month and the miss under light loads returned. Finally the MIL light came on so I had it scanned and was told EGR excessive flow. Again after some searching on here I replaced the pressure sensor with a motorcraft part. After a weekend of driving the MIL light went off so I figured that took care of the excessive flow, but I still had the miss under light load. After a week light came back on, had it read and this time said EGR flow insufficient. I recently purchased the elmscan interface and software from palmer performance but not sure what parameters I should look at to start solving this problem. The miss is getting worse and now it will occur at idle some, but only after truck warms up, runs fin in the mornings for fist few minutes. Any and all help apprecieated

 

egr insufficient flow is usually a DPFE sensor. or egr sensor if you go to napa. look at the hoses to see if they are ripped and if the sensor is broken. thats most likely your problem. get only ford sensor and hoses if necessary.

 

thanks for the reply but I replace the DPFE sensor when I got the EGR excessive flow code, part was replaced with a motorcraft part from Ford. Also if I apply vaccum to the EGR the engine will die so I dont think the ports are clogged.

 

No other suggestions?

 

You need a EGR valve most likley. - If you post the fault numbers (DTC's) , you'll get more feedback.

Yea, when to TB/Plenum hasn't been takin care of (Cleaned) there can be repercussions. The EGR poppet valve is most likley hanging - Hence excessive Flow = 402



Stuck Open Test

Whenever at idle, the PCM checks the voltage of the DPFE sensor and compares it with the voltage recorded by the PCM during the last Key On Engine Off state.

If the voltage is different this indicates a gas flow where none should exist, and the PCM stores the DTC P0402 EGR Flow Excessive Gas Detected. This can cause confusion: in this context excessive flow means there is a flow where none should be detected, ie, the EGR poppet valve has stuck open.



Here's a better look at the valve. Note : The actuating rod is all called the poppet valve.







So - Your valve hanging enough to cause problems is my guess. This weakens the mixture sufficiently enough to cause misfiring, and manifests itself as a noticeable misfire/hesitation at speed and light throttle, not present when accelerating.

 

Jbrew, It through a P00402 for excessive EGR flow a few weeks back. Through a search on here I back probed the differential pressure sensor and was reading over 4 volts with key on engine off, my understanding is taht it shuld have been under 1 volt and increase up to 4 volts as EGR was called for. I replaced the sensor with a new one from Ford and the P0402 code went away, when Iscanned for that code I also found a P0401 for insuficient EGR flow, however I beleive that may have been set when I disconnect the EGR and plugged the line to see if taht affected the miss. I cleared that code and it has not returned.

I still believe it may be a coil, but since I just replaced all with new ones for Global not sure. I am picking up 2 new ones today and plan to swap out 2 at a time to verify if it is a COP issue.

I will also take another look at the EGR system.

Thanks

 

I'd look hard and close for possible vacuum leaks.

 

Ok, another follow up on my problem. The miss has gotten a little worse the last couple days and on the way to work this morning, it flashed the MIl light on three different occasions for about a minute at time, and then again at lunch. I had it scanned expecting a misfire code, and it came up clean no codes stored or pending. Am I wrong in my assumption that a flashing MIK should mean a code was set?

 

Next time she's winking at yuh, just nail it... Push the motor to increase your chances that the monitor is going to catch the fault. That usually works.

 

After a few more trips and the blinking MIL light, it finally set a missfire pending code for cylinder #5. Not sure what it tkeas to actually set that code since the truck was running horrible and shaking bad with tyhe missfire. Anyway I put a new coil on number 5 and running much better. I still beleive I can detyect a slight miss...nad figure another of tyhe coils is going. I plan to go ahead and replace all of the coils I purchase on EBay from Global Automotive. In less than 7 months now I have had at last 2 go bad and believe more are failing. I know otheres posted very good success with those coils on here but that has not been my experience.

 

Did you replace ALL COILS and plugs first time around ??? That's every one at the same time..??

Sounds like you didn't grease them IMO.

 

I am not a fan of those global COP. There is a reason they are so cheap. I know there real popular here but on a few other forums guys have had nothing but troubles with them even when new.

It is possible that some of the egr flow passages are slightly plugged and when the egr comes on it is overloading a cylinder or two which will cause the miss. I know the 4.2 is notorious for this problem. Something to consider if the miss still happens. You may need to pull the egr and plenum and clean out all the passages with coat hanger and Carb cleaner

 

JBrew,

I replaced all at the same time, I figured for the price it was worth trying a set of them. However, I just dont think they have worked out for me. Yes I did grease them. I find other problems contributing later I will update the post.
As a side note, and I am not sure why, but when the scan tool was connected to the ECU and data logging it would go offline anytime the truck started to miss badly, would havbe to restart the scanner and reconnect.

Thanks to everyone for the input.

 

Well this is different - It's already been proven that Globals come from the SAME mother company as the OEM's - It took awhile but someone posted the housing numbers / bottom of the shells.

IMO - You chance of getting bad coils from the get go are posible with any manufacturer. Global still has the best record. I suggest returning them and getting a replacement - it's free.

It's to bad that you had problems. I haven't as of yet, not one in any of the rides I have them in..

Hope you get a good set the next time.

 

I Think I must have read every post on every forum that there is on the internet about this problem and similar ones for the 5.4L Misfire with no DTC.
I am an ASE master Tech and have been for more years then I care to think about.

I have a customer who has a 98 with a problem of misfires with no stored codes which is making me think about retiring very soon. Although I am not one to replace parts without a very good diagnostic that in my mind warrants it. I don’t have the luxury that dealers do, of being able to throw parts and hope it works and the customer pays either way. If I don't fix it The customer doesn't pay. I'm ready to through the kitchen sink on this one.

I grew up servicing cars that had points and plugs and darn little else, I helped to resolve the Cadillac V8-6-4 relocation of the MAP issue when computers in cars were just babies in 1979 and early 80 and by all measure have kept up with emerging technology. So don't sell your ability short in not being able to come up with a positive solution for this one. If I find a solution beyond dynamite that actually does I will post it